Pulse oximetry, combined with clinical observation, provides instant feedback on a patient's status
Chronic respiratory acidosis leads to compensatory metabolic alkalosis
Rapidly tapering vascular shadows accompanied by hyperlucency of the lungs
Electrocardiography can help establish that hypoxia is not resulting in cardiac ischemia and that the underlying cause of respiratory difficulty is not cardiac in nature
Sputum evaluation will show a transformation from mucoid in stable chronic bronchitis to purulent in acute exacerbations
A long, narrow heart shadow
As the disease progresses, hypoxemia worsens and hypercapnia may develop, with the latter commonly being observed as the FEV1 falls below 1 L/s or 30% of the predicted value
Greater sensitivity than standard chest radiography
pH usually is near normal; a pH below 7.3 generally indicates acute respiratory compromise
Increased retrosternal air space
Serum potassium – Diuretics, beta-adrenergic agonists, and theophylline act to lower potassium levels
ABGs provide the best clues as to acuteness and severity of disease exacerbation
Flattening of the diaphragm
Stage IV (very severe): FEV1 less than 30% of predicted or FEV1 less than 50% and chronic respiratory failure
Stage II (moderate): FEV1 50-79% of predicted
Radiographs in patients with chronic bronchitis show increased bronchovascular markings and cardiomegaly
Hematocrit – Patients with polycythemia (hematocrit greater than 52% in men or 47% in women) should be evaluated for hypoxemia at rest, with exertion, or during sleep
Patients with mild COPD have mild to moderate hypoxemia without hypercapnia
Stage III (severe): FEV1 30-49% of predicted
Measure AAT in all patients younger than 40 years, in those with a family history of emphysema at an early age, or with emphysematous changes in a nonsmoker (also see Alpha1-Antitrypsin Deficiency).
Stage I (mild): FEV1 80% or greater of predicted
May help the clinician determine whether surgical intervention would benefit the patient
May provide an adjunctive means of diagnosing various forms of COPD (eg, lower lobe disease may suggest alpha1-antitrypsin (AAT) deficiency
High specificity for diagnosing emphysema (outlined bullae are not always visible on a radiograph)
